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Friction Stir Processing ofAluminum Fusion Welds

Christian Fuller, Murray Mahoney, and

William BingelRockwell Scientific Co.

Funded by: Defense Advanced Research Projects Agency (DARPA), under

contract No. MDA972-02-C-0300, and Dr. Leo Christodoulou, Program Manager

Presented at AeroMat 2003, Dayton, OH, USA - June 9-12, 2003

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OutlineNovember 20, 2003 Chart 2

Introduction

Why Friction Stir Processing (FSP)?

FSP Approaches

AA 6061 Microstructure

Mechanical Properties of AA 5083

Tensile Data

Fatigue Data

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Friction Stir Processing (FSP):November 20, 2003 Chart 3

Is a local thermomechanical process for material propertyimprovement

Has been shown to improve:

Properties of cast Al and NiAl Bronze

The cracking resistance of fusion welded Al

FSP

Base

Material

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Experimental MethodsNovember 20, 2003 Chart 4

In this study we used:

Automated MIG (metal inert-gas) welding

6 mm (single-pass fusion weld) 6061-T651 and 5083-H321

Filler alloy AA 5356

Residual stress measurements - Lambda Research

Fatigue testing- MetCut Research Inc. Tensile testing- Metals Technology

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FSP Approaches for Fusion WeldsNovember 20, 2003 Chart 5

Fusion weld crown FSP

Fusion weld toes FSP

Fusion weld crownand root FSP

Approach 1

Approach 2 Approach 3

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As-Fusion Welded 6061-T651November 20, 2003 Chart 6

Fusion weld

6061 base metal

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As-Fusion WeldedNovember 20, 2003 Chart 7

Fusion Weld, AA 5356 Parent Material, AA 6061

Mg, Si

(Mg2Si?) Al, Fe, Si

(Al5(Fe,Si)?)

Al6(Mn,Fe)

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Weld Toe FSP: MacrographsNovember 20, 2003 Chart 8

6061 base metal

FSP RegionFusion weld FSP Region

FSP Region FSP Region

6061 base metal

Fusion weld

Fusion weld on

retreating side

Fusion weld onadvancing side

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Weld Toe FSP: MicrohardnessNovember 20, 2003 Chart 9

70

75

80

85

90

95

100

105

-8 -6 -4 -2 0 2 4 6

Fusion Weld on Advancing SideFusion Weld on Retreating Side

Vicke

rsmicrohardness(kgmm-2)

Distance from FSP nugget (mm)

FSPFusion Weld(AA 5356)

Parent Material(AA 5083)

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Weld Toe FSP: SEM MicrographsNovember 20, 2003Chart 10

Al6(Mn,Fe)

Mg,Si

Al, Fe, Si

Fusion Weld FSP Region Parent Material

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Weld Crown FSP: MacrographsNovember 20, 2003Chart 11

6061 base metal

FSP Region

Fusion weld

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Surface FinishesNovember 20, 2003Chart 13

Weld Crown FSPAs-Fusion Welded

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Residual Stresses- FSP vs. As-WeldedNovember 20, 2003Chart 15

Parallel to Weld Perpendicular to Weld

-160

-120

-80

-40

0

40

80

120

-60 -40 -20 0 20 40 60

As-Fusion, SurfaceFSP, SurfaceAs-Fusion, 1.6 mm deepFSP, 1.6 mm deep

Distance from fusion weld centerline (mm)

ResidualS

tress(MPa)

-50

0

50

100

150

-60 -40 -20 0 20 40 60

As-Fusion, SurfaceFSP, SurfaceAs-Fusion, 1.6 mm deepFSP, 1.6 mm deep

Distance from fusion weld centerline (mm)

ResidualS

tress(MPa)

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Mechanical PropertiesNovember 20, 2003Chart 16

Fatigue Specimen Tensile Specimen

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Tensile Properties, 5083 Al-4 mm dia. gaugeNovember 20, 2003Chart 17

0

50

100

150

200

250

300

0

5

10

15

20

25

30

y

UTS

E

TensileProperties(M

Pa)

Elongation(%)

As-FusionWelded

Weld ToeFSP

Weld CrownFSP

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Fatigue PropertiesNovember 20, 2003Chart 18

R = 0.1, 30 Hz, load control

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Fatigue Properties-5083/5356November 20, 2003Chart 19

120

140

160

180

200

220

240

104 105 106 107 108

As-Fusion WeldedWeld Toe FSPWeld Crown FSP

MaximumS

tress(MPa)

Number of Cycles to Failure

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Fractured Fatigue Specimens-5083/5356November 20, 2003Chart 20

Weld Toe FSPAs-Fusion Welded

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ConclusionsNovember 20, 2003Chart 21

All FSP approaches (weld toe FSP, weld crown FSP, andweld crown and root FSP) produced a recrystallized, fine-grained microstructure

The tensile properties of AA 5083 were not significantlyeffected by FSP location.

Fatigue resistance of AA 5083 increased with the addition ofFSP.

However, a noticeable difference between the FSPapproaches was not observed.